Electronic ignition system



Dec. 10, 1968 w. A. DAMMANN ELECTRONIC IGNITION SYSTEM Filed June 6,1966 ISTRIBUTOR SCRI FIG.

wmOJU mPZ On ZwaO mPZ O& mic. OmwN INVENTOR WILBUR A DAMM'ANN BY Mafj/MM/ ATTORNEYs United States Patent 3,415,234 ELECTRONIC lGNITIONSYSTEM Wilbur A. Dammann, 1925 N. 65th St.,

Lincoln, Nebr. 68505 Filed June 6, 1966, Ser. No. 555,298 Claims. (Cl.123-148) ABSTRACT OF THE DISCLOSURE An ignition system has a primarycapacitor which is charged when distributor points are closed anddischarged through an ignition coil when the points are opened. Thecharging and discharging of which is under control of the secondary of atransformer with resettable core and the discharge of the capacitor isunder control of a silicon controlled rectifier whose gate is coupledwith a triggering transformer the action of which is dependent on thecharge and discharge of a secondary capacitor, the charging anddischarging of which is under control of the opening and closing of thedistributor points. The circuitry is such that the charging current forthe capacitor by the battery is reduced by utilizing the energy of thecollapsing field of the first transformer.

This invention relates to the operation of internal combustion engines,and is especially adapted for a high performance engine. It moreparticularly relates to an electronic ignition system of the capacitordischarge type and to the electronic circuit used for charging thecapacitor.

A primary object of this invention is to provide for immediate chargingof the capacitor after its initial charge and discharge.

Another object of this invention is to include a triggered siliconcontrolled rectifier in the discharge circuit of the capacitor to theignition coil of the ignition system.

Still another object of this invention is to provide a unique triggeringcircuit for the silicon controlled rectifier dependent on the closing ofthe distributor points.

A further object of this invention is to provide the use of atransformer including a resettable magnetic condition of the core.

These and other objects will become apparent from the followingdescription in conjunction with the accompanying drawing in which:

FIG. 1 is a schematic of an ignition system utilizing the presentinvention; and,

FIG. 2 illustrates various waveforms of the ignition system during theoperation thereof, taken by an oscilloscope reading at the pointsindicated in FIG. 1.

The circuit of FIG. 1 includes as main elements thereof transformers T1and T2, transistors Q1 and Q2, crystal diodes CR1 to CR6 inclusive,silicon controlled diode SCRl, capacitors C1 to C4 inclusive andresistors R1 to R9 inclusive connected into a conventional part of anignition circuit including a batteiy 10, ignition switch 3, ignitioncoil 5, contact points 1 of a distributor and associated spark reducingcapacitor 2. Also there is included as an additional part to theconventional part of the ignition circuit a starting switch 4 movablewith the engine starting switch.

Assuming that capacitor C1 is discharged, as will become later apparentand the starting switch 4 is closed, current will flow from the positivepole of the battery 10 through the switch 4, winding W1 of transformerT1, diode CR3, current limiting resistor R2 and back via ground to thenegative pole of battery 10. This will produce a flux in the core oftransformer T1 in one direction. The transformer T1 is a magneticallyresettable transformer, its core utilizing a memory type offerromagnetic material, that is one in which the direction of magnetismwill be retained until a pulse of current in an associated core willreverse the direction of its magnetism. After the engine had beenstarted and pressure on the starting switch is released, current to theprimary W1 will flow via resistor R1. The resistor R1 is utilized sincewhen the engine is running at battery charging speed, the voltage on thetransformer primary would be higher except for the resistor. The flow ofcurrent Wia resistor R1 is through ignition switch 3.

.As the engine operates, the distributor points periodically close andopen. Starting with the points 1 open, current will flow to thecapacitors C2 and C4 through various paths, the main path being viawinding W2 of transformer T1, through diode 0R4 to capacitor C2 andfurther via resistor R6 to the lower plate of capacitor C4 providing apositive potential which is coupled through capacitor C4 to the bottomof diode 0R6. Capacitor C4 will charge through resistor R7, diode CR6,winding W4 and resistor R8 to ground. See FIG. 2, curve Q). The nextpart of the cycle occurs when the points close. When the closing occursa current pulse through the transformer winding W2 takes place asfollows: from battery 10, positive pole, through winding W2 oftransformer T1, transistor biasing resistor 4, diode CR5, direct currentblocking capacitor C3, charging the capacitor, contact points 1 toground and back to the negative pole of the battery. This results in adrop of potential at the junction of resistor R4 and the base of PNPtransistor Q2, rendering transistor Q2 conductive. When transistor Q2becomes conductive, the potential at the junction of the biasingresistor R3 for P-NP transistor Q1 is lowered, resulting in lowering ofpotential also at the base of transistor Q1 and rendering it conductive.Emitter to base current in cascade can now flow through the transistorsQ1 and Q2 establishing a charging circuit for capacitor C1 as isexplained shortly hereafter. Pun thermore the current strength inwinding W2 is increased by reason of current flow in the collectorcircuits of the transistors aiding the strength of magnetizing currentthrough the winding W2.

The pulse of current in the winding W2 establishes a voltage pulse inthe high voltage secondary W3 of transformer T1 with the upper end ofthe secondary positive resulting in charging the capacitor C1 throughthe following circuit: from the upper end of winding W3 to the capacitorC1 charging the lower plate positive, through the capacitor C1, throughthe winding W2 of transformer T1, the cascaded emitter-base connectionsof transistors Q1 and Q2 and to the bottom of winding W3. This chargingcurrent maintains the bases of the transistors negative and since thecollectors of the transistors are grounded, current flow through thetransistors will be maintained as long as charging current flows throughthe capacitor C1. Upon cessation of current flow, the resistors R3 andR4 will reestablish a positive bias on the bases of the transistors andthey will cut off. The charge on the capacitor C1 is the source ofpotential to create current flow through the primary of ignition coil 5.It cannot discharge otherwise due to the presence of diodes CR1 and CR2.It can discharge through the silicon controlled rectifier SCRl when itsgate is triggered.

The gate to the silicon controlled rectifier is under control of thetrigger transformer T2, associated diode CR6 and capacitor C4 and, ifdesired, of resistance R8 and R9.

Prior to the opening of the distributor points 1, capacitor C4completely discharges through resistance R7, connected to ground, thelower plate of capacitor C4 being grounded through the distributorpoints. The potential remains zero at the junction of capacitor C4 andthe anode 3 of diode CR6, as shown by waveform #7, FIG. 2, until thepoints open.

When the points open, capacitor C4 having been completely dischargedthrough resistance R7 when the points were closed, a positive pulse dueto the current provided through resistor R6 is coupled through capacitorC4 and diode CR6 to the primary winding W4 of transformer T2 providing aproper pulse to gate the silicon controlled rectifier SCRl. The pulsetriggers silicon controlled rectifier SCRl into conduction and thecharge on capacitor C1 discharges through the primary winding W6 of theignition coil 5, thereby providing the required high voltage output tothe distributor. Silicon controlled rectifier SCRl remains conducting ascapacitor C1 discharges through zero and during the time the ignitioncoil reverses polarity due to flywheel action or ringing. When theignition coil reverses polarity, capacitor C1 is charged negative withrespect to diodes CR1 and CR2, and silicon controlled rectifier SCRlcuts off during the time that the field of the ignition coil collapsesin the positive direction.

The charge on capacitor C1 (now negative at the bottom of C1 asrepresented on the schematic) will try to discharge through diodes CR1and CR2, but winding W3 of transformer T1 offers a higher impedance thanwinding W1; therefore, capacitor C1 will discharge through diode CR1 andwinding W1 of transformer T1. This discharge current resets thedirection of flux in the memory core of transformer T1. Diode CR3 isreverse biased, thereby preventing loss of reset current throughresistor R2.

At the time of reset, the positive pulse occurring at the bottom ofwinding W2 of transformer T1 is coupled through diode CR4 to chargecapacitor C2. The current is provided by transformer action from windingW2 of transformer T1 through the diode CR4 and capacitor C2, chargingthe upper plate of capacitor C2 positive. This reverse biases diode CR7,thereby eliminating any possibility of noise pulses coming from theprimary power source to trigger the system. As soon as the core oftransformer T1 is saturated, the EMF collapses and reverses polarityproviding a negative polarity at the lower terminal of winding W3 oftransformer T1 and the base of transistor Q2. The charging current forcapacitor C1 at this time is provided by the energy of the collapsingfield of transformer T1. By providing this initial charge, the currentrequired from the primary power source is decreased and therefore thecapacitor C1 charges faster. This polarity then starts the chargingcycle of capacitor C1 through the conduction of transistors Q1 and Q2 aspreviously described. By using this recharging means for capacitor C1,the complete cycle time is shorter thereby increasing the possiblemaximum r.p.m. of the engine.

After the initial charging of capacitor C1, closing of the points 1 hasno effect on the circuit operation, except to insure that capacitor C1is charged, because capacitor C1 is normally charged immediately afterdischarge and is discharged when the points open, thereby keepingcorrect timing.

It is pointed out that resistors R8 and R9 in the transformer circuit T2are provided to eliminate possible noise impulses feeding back from thecoil.

Resistor R5 provides a slow discharge path for direct current blockingcapacitor C3. R6 provides a charging current path for capacitor C4 atthe time the points open. Resistor R7 provides a time constant toprevent positive pulses from being felt at transformer T2 due topossible point bounce.

The function of capacitor C2 is to provide a potential greater than thebattery supply potential to reverse bias diode CR5 when the points areopen (non conducting).

When diode CR5 is reverse biased, no signal, pulse or noise can bepassed from any external source through diode CR5 to falsely triggertransistor Q2 into conduction.

Capacitor C2 is charged after the points open, during the reset time oftransformer T1.- R ferring to FIG. 2,

waveforms #3 and #4, a positive pulse is present at the bottom ofwinding W2 a short time microseconds) after the points open. Thispositive pulse (approximately 40 volts) is coupled through diode CR4 andapplied to capacitor C2, charging capacitor C2 to a positive potential(approximately 40 volts).

The function of diodes CR4 and CR7 is to enable capacitor C2 to hold itscharge. After capacitor C2 is charged to a positive potential, which isgreater than the battery potential, diodes CR4 and CR7 will be reversebiased also, enabling capacitor C2 to hold its charge as long as thepoints are open.

As can be seen in FIG. 1, the bottom of capacitor C4 will charge to thesame potential. With the use of diodes CR4, CR5, CR7 when the points areopen, there will not be a discharge path for capacitor C2.

The graph of FIG. 2 illustrates the various waveforms monitored atindicated points of FIG. 1, starting with the negative pulse appliedwhen the distributor points are closed and the end result of the highvoltage output applied to the distributor by the discharging ofcapacitor C1 when the points 1 are opened.

The system of the invention outperforms other systems tested withrespect to output voltage, and the maintenance of higher output voltageat the higher r.p.m.s.

It will be obvious to one skilled in the art that various changes may bemade in the invention without departing from the spirit and scopethereof, and therefore the invention is not limited by that which isillustrated in the drawing and described in the specification, but onlyas indicated in the accompanying claims.

What is claimed is:

1. A capacitor charging and discharging ignition system comprising:

a .power source;

breaker points in series with said power source;

a primary charging capacitor and an ignition coil;

a magnetically resettable transformer including first,

second, and third windings;

an initial current path from said power source through a first diode andsaid first winding to said power source thereby providing an initialsetting of said transformer in a proper magnetic condition;

a charging means for said primary capacitor operable on the closure ofsaid breaker points and including a switching means in series with saidsecond winding and said breaker points thereby providing an inducedvoltage in said third winding and allowing current to charge saidprimary capacitor through said third winding, said switching means andsaid second wind- 2;;

a switching device connected between said primary capacitor and saidignition coil, said switching device having activating means, saidswitching device preventing discharge of said primary capacitor to saidcoil unless said activating means is operated, said switching deviceproviding a first discharge path for said primary capacitor through saidignition coil thereby producing an output for ignition purposes, saidswitching device remaining activated after the discharge of said primarycapacitor thereby allowing said primary capacitor to be charged bycurrent from said ignition coil;

a second discharge path for discharging said primary capacitor includinga third diode and said first winding thereby resetting the magneticcondition of said transformer, the discharging of said primary condenserby said second discharge path providing a partial charging current forsaid primary capacitor from the collapsing field of said transformerthereby allowing a faster recharge of said primary capacitor.

2. A capacitor charging and discharging ignition system as in claim 1and wherein said switching device includes a gated silicon-controlledrectifier.

3. A capacitor charging and discharging ignition system as in claim 2and wherein said silicon-controlled rectifier is gated on through apulse transformer when said breaker points open.

4. A capacitor charging and discharging ignition system as in claim 1and wherein said switching means includes series connected transistorswitches 5. A capacitor charging and discharging ignition system as inclaim 4 and wherein said transistor switches include resistive biasingmeans to render said transistor switches non-conductive.

6. The invention of claim 1, and wherein said actuating means for saidswitching device includes an inhibiting means for said actuating means,said inhibiting means including a resistor-capacitor network, saidnetwork including a discharge path during the time that said breakerpoints are closed, thereby providing a time constant to preventactuation of said actuating means due to possible point bounce.

7. The invention of claim 6, and wherein said capacitor and a diodeprovide a coupling path to actuate said switching device.

8. The invention of claim 1, and wherein said activating means includesa pulse transformer including a primary winding in series with a diodeand a coupling capacitor, said pulse transformer including a secondarywinding connected to said switching device, said actuating means therebyproviding the coupling of a pulse from said primary winding to saidsecondary winding to activate said switching device when said pointsopen.

9. An ignition system of the capacitor charge and discharge typecomprising:

a power source;

a pair of breaker points in series with said power source; a chargingcapacitor and an ignition coil; a switching means to control thedischarge of said charging capacitor; a transformer; means provided tocharge said capacitor through said transformer; and, means responsive tothe discharge of said capacitor through said coil to provide a partialrecharge of said capacitor through said transformer. 10. An ignitionsystem as in claim 9 and wherein said transformer includes a coreallowing a settable and resettable magnetic condition.

References Cited UNITED STATES PATENTS 3,150,286 9/1964 Quinn. 3,2A2,4203/ 1966 Ulrey. 3,263,124 7/1966 Stuermer. 3,309,568 3/ 1967 Nilssen.3,312,210 4/1967 Nilssen. 3,318,296 5/1967 Hufton. 3,329, 867 7/1967Stearns.

LAURENCE M. GOODRIDGE, Primary Examiner.

US. Cl. X.R.

